Field of the Invention
The present invention relates to a printing apparatus for printing an image on a sheet, a control method for the printing apparatus, and a storage medium.
Description of the Related Art
There is an image forming apparatus that reads a chart with a black image having a predetermined width being printed thereon in advance by using an auto document feeder (ADF) to diagnose misregistration at a leading edge (see Japanese Patent Application Laid-Open No. 2005-176045).
To read a document by using an ADF, for example, a document placed on a document tray of the ADF is conveyed while an image of the document is read at a fixed position of an optical system. To read a document by using a document positioning plate, for example, a document placed on the platen glass (document positioning plate) is fixed while an optical system is moved to read an image of the document.
For example, when images of a plurality of documents are read, it is more desirable to use the ADF for reading them than to use the document positioning plate for reading them. The reason is that the plurality of documents can be placed on the document tray of the ADF and the documents can be separated and conveyed one by one. This can reduce time taken for a user repeatedly placing the documents.
An amount of shift of a printing position depends on physical properties of the sheet to print. Thus, for example, when a shift in the printing position with respect to a sheet of high grammage is checked, a black image having a predetermined width needs to be printed on the sheet of high grammage to output a chart. The chart of high grammage is more desirably read by using the document positioning plate than by using the ADF. The reason is that the chart of high grammage is difficult to bend, and when the chart is conveyed from the document tray of the ADF, the chart may fail to form a loop and can cause a jam on the way.
However, the image forming apparatus discussed in Japanese Patent Application Laid-Open No. 2005-176045 scans a chart by using the ADF to diagnose misregistration at the leading edge. As a result, with a technique discussed in Japanese Patent Application Laid-Open No. 2005-176045, a jam can occur when a specific chart is scanned (for example, chart of high grammage) by the ADF, and the amount of shift of the registration at the leading edge may fail to be obtained.